also shell-fish, "animal that lives in the water and has a shell," Old English scylfiscas (plural); see shell (n.) + fish (n.) in the old general sense of "aquatic animal."
Entries linking to shellfish
shell n.
"hard outer covering," Middle English shel, shelle, from Old English sciell, scill, Anglian scell "seashell; eggshell," which is related to Old English scealu "shell, husk," from Proto-Germanic *skaljo "piece cut off; shell; scale" (source also of West Frisian skyl "peel, rind," Middle Low German schelle "pod, rind, egg shell," Gothic skalja "tile"), with the shared notion of "covering that splits off," from PIE root *skel- (1) "to cut." Italian scaglia "chip" is from Germanic.
Also in late Old English as "a coating or layer." The general sense of "protective outer covering of some invertebrates" is in Middle English (by c. 1400 as "house of a snail;" by 1540s in reference to a tortoise or turtle); the meaning "outer layer of a nut" (or a fruit considered as a nut) is by mid-14c. With notion of "mere exterior," hence "empty or hollow thing" by 1650s. The meaning "hollow framework" is from 1791; that of "structure for a band or orchestra" is attested from 1938. To be out of (one's) shell "emerged into life" is by 1550s.
Military use for "explosive projectile" is by 1640s, first of hand grenades, and originally in reference to the metal case in which the gunpowder and shot were mixed; the notion is of a "hollow object" filled with explosives. Hence shell shock, "traumatic reaction to the stress of battle," recorded by 1915.
Shell game "a swindle" is from 1890, from a version of the three-card game played with a pea and walnut shells.
fish n.
"a vertebrate which has gills and fins adapting it for living in the water," Old English fisc "fish," from Proto-Germanic *fiskaz (source also of Old Saxon, Old Frisian, Old High German fisc, Old Norse fiskr, Middle Dutch visc, Dutch vis, German Fisch, Gothic fisks), perhaps from PIE root *pisk- "a fish." But Boutkan on phonetic grounds thinks it might be a northwestern Europe substratum word.
Popularly, since Old English, "any animal that lives entirely in the water," hence shellfish, starfish (an early 15c. manuscript has fishes bestiales for "water animals other than fishes"). The plural is fishes, but in a collective sense, or in reference to fish meat as food, the singular fish generally serves for a plural. In reference to the constellation Pisces from late 14c.
Fish (n.) for "person" is from 1750 with a faintly dismissive sense; earlier it was used in reference to a person considered desirable to "catch" (1722). Figurative sense of fish out of water "person in an unfamiliar and awkward situation" attested by 1610s (a fisshe out of the see in the same sense is from mid-15c.). To drink like a fish is from 1744. To have other fish to fry "other objects which invite or require attention" is from 1650s. Fish-eye as a type of lens is from 1961. Fish-and-chips is from 1876; fish-fingers from 1962.